import java.util.LinkedList;
import java.util.Scanner;

public class Main {


    //重排字符串
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        char[] s = in.next().toCharArray();
        char maxChar = '0';
        int maxCount = 0;
        int[] hash = new int[26];
        for (int i = 0; i < n; i++) {
            char ch = s[i];
            if (++hash[ch-'a'] >maxCount){
                maxCount = hash[ch-'a'];
                maxChar = ch;
            }
        }
        if (maxCount>(n+1)/2){
            System.out.println("no");
        }else{
            System.out.println("yes");

            char[] ret = new char[n];
            int i = 0;
            while(maxCount-- !=0){
                ret[i] = maxChar;
                i+=2;
            }
            for (int j = 0; j < 26; j++) {
                if(hash[j]!=0 &&(char)(j+'a')!=maxChar){
                    while(hash[j]-- !=0){
                        if (i>=n) i = 1;
                        ret[i] = (char)(j+'a');
                        i+=2;
                    }
                }
            }
            for (int j = 0; j < n; j++) {
                System.out.print(ret[j]);
            }
        }
    }






    //最长无重复子数组
    public int maxLength (int[] arr) {
        LinkedList<Integer> list = new LinkedList<>();
        int res = 0;
        for (int i = 0; i < arr.length; i++) {
            if(list.contains(arr[i])){
                int j = list.indexOf(arr[i]);
                while(j-->=0){
                    list.removeFirst();
                }
            }
            list.add(arr[i]);
            res = Math.max(res,list.size());
        }
        return res;
    }




    //牛牛冲钻五
    public static void main1(String[] args) {
        Scanner in = new Scanner(System.in);
        int t = in.nextInt();
        for (int i = 0; i < t; i++) {
            int n = in.nextInt();
            int k = in.nextInt();
            char[] ch = in.next().toCharArray();
            int ret = 0;
            for (int j = 0; j < ch.length; j++) {
                if(ch[j] == 'L') ret-=1;
                else{
                    if(j-1>=0 && j-2>=0 && ch[j-1] == 'W' && ch[j-2] == 'W'){
                        ret+=k;
                    }else ret+=1;
                }
            }
            System.out.println(ret);
        }
    }

}
